Nervous System Exam 1 Flashcards
What are the two divisions of the nervous system and what are they composed of
Central Nervous System: brain and spinal cord
Peripheral Nervous System: nerves that connect the brain or spinal cord with the body’s muscles, glands, sense organs, tissues
What are the two types of principle cell types of the nervous system
Neurons and Glial Cells
What are neurons
-Functional units of the nervous system
-Excitable cells that transmit electrical signals from one cell to another
-Do NOT DIVIDE
Parts of Neurons:
Dendrites
Cell Body
Node of Ranvier
Schwann Cells
Dendrites: receive signals from other cells
Cell Body: organizes and keeps cell functional
Node of Ranvier: Allow diffusion of ions
Schwann Cells: produces the myelin sheath
Parts of Neurons:
Axon
Axon Hillock
Axon Terminal
Myelin Sheath
Axon: transfers signals to other cells and organs
Axon Hillock: generates impulse in the neuron
Axon Terminal: forms junctions with other cells
Myelin Sheath: increases the speed of the signal
Axonal Transport:
cellular process responsible for movement components to and from the soma
Anterograde transport vs Retrograde transport
Anterograde: from soma to axon terminal
Retrograde: from axon terminal to soma
Retrograde Transport
Fast transport:
-moves membrane vesicles and cellular material to be degraded
-moves substances that enter the neuron
-mediated by dynein
Anterograde Transport
Slow axonal transport
-moves neurofilaments and microtubule proteins
Fast axonal transport
-moves organelles with membranes along the surface of microtubules
-mediated by kinesin
Neurons are classified based on structure and function define each
Structural classification: according to the number of processes extending the body
Functional classification: based on the direction of the nerve impulse with respect to the CNS
Multipolar Neurons
several short dendrites and a single long axon (neuron in the brain and in the spinal cord)
Bipolar Neurons
Single axon and one main dendrites
Unipolar Neurons
have cell body to one side and a single axon divided into branches (sensory neurons in skin, muscles, joints)
Afferent Neurons or Sensory
From receptors on organs to the CNS (brain)
Unipolar
Interneurons
connect sensory neurons and muscles
located in CNS
multipolar
Efferent Neurons or Motor
Info from CNS to periphery organs
effectors are muscles and glands
multipolar
How do glial cells support neurons (neuroglia)
-form myelin sheath around neuronal axons
-making the cerebrospinal fluid
-participating in phagocytosis (eating of things)
-Blood-Brain Barrier
Types of glia cells in PNS and CNS
PNS: satellite cells, schwann cells
CNS: oligodendrocytes, astrocytes, microglia, ependymal cells
Satellite Cells in PNS
-surround neuron cell bodies in ganglia
-regulate O2 and CO2 nutrient, and neurotransmitter levels around neurons in ganglia
(surround the body of neurons and get rid of things)
Schwann Cells in PNS
-surrounds axons ONE at a time
-responsible for myelination of peripheral axons
-participate in the repair process after injury
Oligodendrocytes in CNS
-myelinate axons
-structural framework
- surrounds many axons at once
- has small cell bodies
Astrocytes in CNS
-BBB
-structural support
-regulate ion, nutrient, gas concentration
-absorb and recycle neurotransmitters
-form scar tissue after injury
Microglia Cells in CNS
remove cell debris, waste, and pathogens by phagocytosis
Ependymal Cells in CNS
-Line ventricles (brain) and the central canal (spine)
-Assist in producing, circulating, and monitoring of CSF
BBB
-semi-permeable
-composed of blood vessels and glial cells, tight junctions
-astrocytes processes cover capillaries
-joins cell walls of vessels
-prevent diffusion of material between endothelial cells
What is myelination and what is it composed of
It is the process of forming a myelin sheath which increases nerve impulse speed
80% lipids, 20% proteins and water
How is myelination formed in CNS and PNS
CNS - oligodendrocytes
PNS - Schwann Cells
Myelination in CNS axons
cell bodies of oligodendrocytes do not surround the axons
no neurolemma formed
involved in forming myelin sheath
synthesis of large amounts of plasma membrane
Unmyelinated Axons in PNS
bundle of axons that are wrapped very thinly by Schwann cells
Node of Ranvier
Gaps in myelin sheath
facilitates in rapid conduction of nerve impulses
electrical impulses hop node to node
important in signal transduction
Electrical signals in neurons depends on what two things
depends on the variety of ion channels
existence of resting membrane potential
Types of ion channels
Leaky - random open and close
Gated - ligand, mechanically, voltage
Where are leaky channels in neurons
dendrites
can be in cell bodies and axons
Where are ligand-gated channels located
in dendrites of sensory neurons
in dendrites and cell bodies of interneurons and motor neurons (at synapse)
Where are mechanically gated channels located
auditory receptors, internal organs, skin
-vibration, touch, pressure
Where are voltage-gated channels located
mainly neuronal axon
unmyelinated axons, Node of Ranvier (myelinated), axon hillock
What are nerve impulses
electrical signals by which neurons talk to one another and other cells of the body
What are nerve impulses also referred to as
action potential: brief reversal of the membrane potential
Depolarization
Repolarization
Hyperpolarization
Depolarization: potential moves from RMP to less negative or positive values
Repolarization: potential returns to the RMP (negative)
Hyperpolarization: potential moving away from the RMP in a more negative direction
When there is RMP how is it stimulated
No stimulation, no nerve imoulse
What two things does the magnitude of RMP depend on
Differences in specific ion concentrations inside and outside the cell
Differences in membrane permeability to the different ions –> number of open channels
What two things does the Goldman Field equation consider
concentration of ion inside and outside the cell
permeability
What does the Nernst Equation predict
equilibrium potential
What does action potential depend on
-Distribution of ions
-Changes in membrane permeability to ions
-It is short-lasting
What happens in each of the 6 stages of resting membrane potential and action potential
1: Resting membrane potential
2: Depolarization makes less negative Na+ leaks in
3: All channels of Na+ are open (-) to (+)
4: Na+ close and K+ open (+) to (-)
5: Not all K+ close at once, hyperpolarization
6: action potential, goes back to the starting point
Does the action potential change with different amounts of stimulus within a cell
no, the amplitude is always the same
How are refractory periods a safety mechanisms
system can only open with enough closed pumps
What is an absolute refractory period
Channels are in the open and inactive state which can not create a action potential because more channels can not open
What is a relative refractory period
Pumps are in the closed and inactive state which with enough stimulus can open pumps
What is continuous propagation
non-myelinated axons
ions flow to adjacent segments
short distance
slow
What is saltatory propagation
myelinated axons
action potentials in nodes of ranvier
action potentials jump from node to node
faster
What is synaptic transmission
a neuron communicates with a target cell across a synapse
What are electrical synapses
allows ions to move through one neuron to another through gap junctions
What are chemical synapses (steps of Ca2+)
-Needs Ca to depolarize (pre-synaptic)
-increase of Ca vesicles move
-fuse vesicles to the membrane and makes pore
-neurotransmitters leave in synapse and move to other cell to produce an effect (post-synaptic)
-creates an action potential
What are the three types of chemical synapses
Axodendritic: Axon and dendrite
Axosomatic: axon and somatic
Axoaxonic: axon and axon
Nerve impulse vs synaptic transmission
Nerve Impulse: production of action potential, change in membrane potential, flow of ions
Synaptic transmission: release neurotransmitters at the synapse
Neurotransmitters are what kind of messengers
chemical messengers
Difference between excitatory and inhibitory transmitters
EPSP: promotes an action potential in receiving neuron (Ca+2)
IPSP: prevents an action potential (Cl- or K+)
What are the three types of removal of neurotransmitters (after effects)
-Reuptake: NT is transported back to presynaptic terminal, transport into nearby glial cells to get degraded
-Enzymatic Transformation: at the synaptic cleft (acetylcholine), inside the cell
-Diffusion: away from active site
*All are metabolized to get rid of, or they can be reused
Ionotropic:
Receptor
Speed
Function
Effect
Example
Ligand-gated
Fast
The functional domain of extracellular NT binding site and membrane-spanning domain forms ion channels (+)
Effect: depolarization or hyper-polarization
Ex: Acetylcholine
How does depolarization and hyper-polarization relate to an excitatory and inhibitory transmitter
depolarization: excite (ESPS)
hyper-polarization: inhibit (ISPS)
Metabolic Receptor
7 times through the membrane
slow
GCPRs
specific amino acids
*ion channel not apart of the receptor
How does a GCPR work Directly
- Ligand binds to receptor
- Exchange GDP for GTP on alpha
- Dissociation between alpha and beta/gamma
- Subunits bind to effectors (can inhibit or activate) - alpha to E
- Hydrolysis of GTP to dissociate subunits from effectors
- Formation of inactive state (subunits bind to GCPR)
How does GCPR work indirectly
NT binds to receptor
G protein binds to an effector (adenylyl cyclase)
uses cAMP as a second messenger
protein kinase
activate channel
In GCPRs what is the state when there is positive vs negative charged
positive: active (positive charges into the cell)
negative: inactive
Three postsynaptic potentials
Graded: small changes in membrane potential (small stimulus)
Magnitude: depends on stimulus (number of channels)
Summation: channels added together (small openings close enough to produce AP)
CNS functions
Voluntary movement: muscle contraction
Involuntary movement: breathing
Process sensory information: pain
Source of thoughts
What are the three layers of the meninges
Dura Mater (outermost)
Arachnoid Mater (middle) *
Pia Mater (inner) *
*CSF liquid between the two (continually made and into blood stream)
Ventricles
cavities with CSF to cushion brain and spine
What is the space between the Pia Mater and Arachnoid Mater called
subarachnoid
What is the importance of the CSF
provide nutrients
maintain electrolyte balance for neurons
clears waste
regulate intracranial pressures
What are in the external and internal portions of the brain
External:
Cerebrum
Brainstem - midbrain, pons, medulla oblongata
Cerebellum
Internal:
Diencephalon - thalamus, hypothalamus
Thalamus
The upper part of the diencephalon
Central Relay Station: motor and sensory signals to cortex
Regulates sleep and focus
Damage can lead to coma
Hypothalamus
Below the thalamus
Maintain homeostasis (heart rate, temp, thirst)
influences the endocrine system by pituitary gland
Pituitary Gland
bottom of hypothalamus
“master gland” controls release of hormones that maintain homeostasis
Pineal Gland
roof of diencephalon
produces melatonin (sleep regulator)
Brain Stem 3 major parts
Midbrain: visual and auditory reflex
Pons: part of respiratory center
Medulla Oblongata: cardiac center (heart rate), vasomotor center (blood pressure), respiratory center
*Site of cranial nerves (PNS)
Spinal Cord (CNS)
Long, thin, tubular bundle of nervous tissue
Functions:
-axons take sensory information into the brain
-motor info: neurons from brain & axon synapse to different muscles
Coordinates reflex actions w/out brain
Functions:
Cervical
Thoracic
Lumbar
Sacral
Coccygeal
Cervical: innervate hands, arms
Thoracic: innervate organs in upper chest and upper abs
Lumbar: Innervate organs in lower abs, hips, legs
Sacral: Innervate genitals and lower digestive track
Coccygeal: Innervate skin
What are PNS two main systems
Autonomic Nervous System: involuntary, regulates organs and tissues
Somatic Nervous System: Voluntary, skeletal muscle
PNS detects _______ and transmits information to the ___ and receive information from the ___
Stimuli, CNS, CNS
What are the three divisions in the autonomic nervous system
Sympathetic: mobilizes body (fight or flight)
Parasympathetic: conserves energy (rest and digest)
Enteric: regulates GI track
Most organs have duel intervention by sympathetic and parasympathetic systems. What are the two exceptions and which system are they located in
Blood vessels, sweat glands,
Sympathetic (can’t completely shut down)
ANS has two neurons, what are they called
Preganglionic neuron from spinal cord and a postganglionic neuron
Where are the two synapses in ANS
Between preganglionic and postganglionic
Between postganglionic and effector (organ, tissue, gland)
ACh is released by preganglionic in both ANS systems. In the postganglionic which releases ACh and which system releases NE and E
Parasympathetic: acetylcholine
Sympathetic: norepinephrine, epinephrine
Length of synapses for sympathetic and parasympathetic and which receptor they use
sympathetic: short –> long, adrenergic
parasympathetic: long –> short, cholinergic
Fight or flight response sympathetic pathway functions (10)
Dilate Pupils*
Inhibit Salvation
Increase Heartbeat*
Relax Airways (get air in)*
Inhibit Stomach Activity*
Release Glucose/ Inhibit Gallbladder
Inhibit Intestines*
Secrete E and NE
Relax bladder*
Genital contraction
Two systems only have one neuron (preganglionic) what are they
Somatic system
Adrenal System
Somatic system
Preganglionic projects directly from CNS to skeletal muscle
Motor neurons are myelinated
NT is ACh (Na+ channel)
Muscle Contraction and Tissues
Adrenal system
Sympathetic System
Preganglionic innervate chromaffin cells in medulla release ACh
ACh bind to nicotinic receptors
Releases E and NE get in blood vessels and go to organs aka hormones
